Based on the goal of green and effective removal of chromium (Cr(VI)) pollution in water and the idea of treating waste with waste, rice straw (RS) was firstly and successfully used in enhancing the photoreduction of highly toxic Cr(VI) to less toxic Cr(III) by oxalic acid (Ox). Batch experiments (the effect of Ox concentration, initial Cr(VI) concentration, RS dosage and coexisting ions) in Ox + RS + UV photoreduction system were designed to investigate the reaction process. Through studying the effect of initial pH in the solution, the change of pH during the photoreduction process and the free radical scavenging test, the Cr(VI) photoreduction mechanism in Ox + RS + UV system was revealed. The role of RS in Ox + RS + UV system was also deduced by the analysis of FT-IR, XRD, Mott-Schottky and the verification test of the role of –OH and SiO₂ on RS. The results showed that RS could significantly synergize Ox to reduce Cr(VI) under UV, 1 mM Cr(VI) in aqueous solution was completely removed in 60 min by Ox + RS + UV system. The Cr(VI) photoreduction mechanism in Ox + RS + UV system consisted of multiple parts: the chemical reduction by Ox(few part), the photoreduction by Ox(some part), and the synergistic photoreduction by RS with Ox(large part). The synergism of RS in Ox + RS + UV system was mainly attributed to its components of SiO₂ and –OH of cellulose.

In this paper, the acute toxicity of monobutyl phthalate (MBP), the main hydrolysis product of dibutyl phthalate, on adult zebrafish liver antioxidant system was studied. Compared the toxicity effect of MBP and DBP by histopathology and apoptosis experiments, we speculated that the toxic effects of DBP on animals may be caused by its metabolite MBP. The results indicated that the antioxidant Nrf2-Keap1 pathway was insufficient to resist MBP-induced hepatotoxicity and led to an imbalance of membrane ion homeostasis and liver damage. Decreased cell viability, significant tissue lesions and early hepatocyte apoptosis were observed in the zebrafish liver in MBP exposure at high concentration (10 mg/L). The activities of antioxidant enzymes and ATPases in zebrafish liver were inhibited with increased malondialdehyde (MDA) content and alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities. Integrated biomarker response (IBR) calculation results indicated that MBP mainly inhibited catalase (CAT) activity. Simultaneously, the expression of antioxidant-related genes (SOD, CAT, GPx, Nrf2, HO-1) was down-regulated, while apoptosis-related genes (p53, bax, cas3) were significantly up-regulated.

Tris (1,3-dichloro-2-propyl) phosphate (TDCPP) is a type halogenated organophosphate flame retardants (OPFRs), which has been identified as contaminants of emerging concern (CECs). The use and production of OPFRs began to increase gradually when brominated flame retardants (BFRs) were banned. Halogenated OPFRs, especially TDCPP have been considered to lead to mutagenicity and carcinogenesis and major concerns have been raised regarding their toxicity. In this study, the toxicity effects and mechanisms of TDCPP were summarized and ecological risk assessment was made regarding its potential impact on freshwater organisms. TDCPP has been widely detected in ecosystems throughout the world, with observed toxicity effects on both humans and freshwater organisms. Inhalation of the dust was found to be the main exposure for humans. TDCPP could be metabolized in the human body, and medium stability was achieved in human body with the main metabolite BDCPP. Aside from mutagenicity and carcinogenesis, TDCPP was also found to have the potential for endocrine disruption and impairing the human reproductive system. Furthermore, this study reviewed the results of previous toxicity experiments, including acute toxicity, growth and development toxicity, neurotoxicity, and hepatotoxicity in freshwater organisms. Risk assessment was made using the safety threshold method by comparing the toxicity data with the exposure data in freshwater. HC₅ (hazardous concentration for 5% of organisms) derived based on traditional endpoints of acute toxicity LC₅₀ (median lethal concentration) or EC₅₀ (concentration for 50% of maximal effect) was 877 μg/L. This value was much higher than the exposure concentration levels in the surface water with EXD₉₀ (exposure data with cumulative probability 90%) of 65.22 ng/L. However, based on the growth and development toxicity data, the derived HC₅ was 33.33 ng/L and the calculated MOS (margin of safety) was below 1. Therefore, the results validated the fact that the ecological risk of TDCPP could not be neglected for its growth and development toxicity.

The effects of dike construction on the geomorphology and sedimentary processes of tidal flats were investigated using high-precision topographic profiling, short cores, and unmanned aviation vehicle (UAV)-assisted photogrammetry to understand their adverse consequences on the benthic ecosystem. Tidal flats at the south of Shinsi Island near one of the two sluice gates of the Saemangeum dike, display prominent morphologic features known as shelly sand ridges or cheniers (sensu Otvos, 2000) that have migrated landward about 5 m in a year. The tidal flats were dominated by erosion from winter to spring and by deposition during the remainder of the year except for the periods of heavy precipitation when tidal drainage channels became larger and deeper by headward erosion. With overall coarser-grained surface sediments, the presence of actively migrating wave-built cheniers are in stark contrast to muddy tidal flats with a monotonous morphology before the completion of the Saemangeum dike in 2006. Southeasterly waves reflected from the dike during winter to spring when north to northwesterly winds prevail account for the wave-induced onshore sediment transport and rapid morphologic changes in the tidal flats despite their location protected from offshore waves. The diversity and biomass of major macrofauna species tend to increase during rapid erosion and decrease during rapid deposition, highlighting the anthropogenic effect of dike-induced physical disturbance on the benthic ecosystem in the otherwise sheltered tidal flats.

Chemical analysis of plasma samples of wild fish from the Sava River (Croatia) revealed the presence of 90 different pharmaceuticals/illicit drugs and their metabolites (PhACs/IDrgs). The concentrations of these PhACs/IDrgs in plasma were 10 to 1000 times higher than their concentrations in river water. Antibiotics, allergy/cold medications and analgesics were categories with the highest plasma concentrations. Fifty PhACs/IDrgs were identified as chemicals of concern based on the fish plasma model (FPM) effect ratios (ER) and their potential to activate evolutionary conserved biological targets. Chemicals of concern were also prioritized by calculating exposure-activity ratios (EARs) where plasma concentrations of chemicals were compared to their bioactivities in comprehensive ToxCast suite of in vitro assays. Overall, the applied prioritization methods indicated stimulants (nicotine, cotinine) and allergy/cold medications (prednisolone, dexamethasone) as having the highest potential biological impact on fish. The FPM model pointed to psychoactive substances (hallucinogens/stimulants and opioids) and psychotropic substances in the cannabinoids category (i.e. CBD and THC). EAR confirmed above and singled out additional chemicals of concern - anticholesteremic simvastatin and antiepileptic haloperidol. Present study demonstrates how the use of a combination of chemical analyses, and bio-effects based risk predictions with multiple criteria can help identify priority contaminants in freshwaters. The results reveal a widespread exposure of fish to complex mixtures of PhACs/IDrgs, which may target common molecular targets. While many of the prioritized chemicals occurred at low concentrations, their adverse effect on aquatic communities, due to continuous chronic exposure and additive effects, should not be neglected.

Disastrous oil spills cause severe environmental issues. The shortcomings of current cleaning methods for remediating oil have prompted the latest research drive to create intelligent nanoparticles that absorb oil. We, therefore, synthesized 197 ± 50 nm floatable photoreactive hybrid nanoparticles with Ag–TiO₂ plasmonic photocatalyst (Eg = 3.08 eV) content to eliminate interfacial water pollutants, especially toluene-based artificial oil spill. We found that the composite particles have non-wetting properties in the aqueous media and float easily on the surface of the water due to the moderate hydrophobic nature (Θ = 113°) of the matrix of polystyrene, and these properties lead to elevated absorption of the interfacial organic pollutants (e.g., mineral oil). We showed that (28.5 mol%) divinylbenzene cross-linker content was required for adequate swelling capacity (2.15 g/g), whereas incorporated 15.8% Ag–TiO₂ content in the swollen particles was enough for efficient photodegradation of the artificial oil spill under 150 min LED light (λₘₐₓ = 405 nm) irradiation. The swollen polymer particles with embedded 32 ± 7 nm Ag–TiO₂ content increase the efficiency of photooxidation by increased the direct contact between both the photocatalysts and the artificial oil spill. Finally, it was also presented that the composite particles destroy themselves: after approximately one and a half months of continuous LED light irradiation, the organic polymer component of the composite was almost completely (88.5%) photodegraded by the incorporated inorganic photocatalyst particles.

Cadmium (Cd) is a heavy metal of concern in contaminated sites because of its high toxicity to soil biota and humans. Typically, Cd exposure is thought to be dominated by dissolved Cd in soil pore water and, thus, dermal uptake. In this study, we investigated the uptake, toxicity, and maternal transfer of Cd in a standard soil invertebrate, the oribatid mite (Oppia nitens), which is common to boreal and temperate ecozones. We found total soil Cd predicted Cd uptake in adult and juvenile O. nitens with no significant uptake from pore water by juvenile mites. Cadmium significantly inhibited juvenile production and recruitment as well as reduced adult fecundity. Adult O. nitens maternally transferred 39–52% of their Cd body burden to juveniles (tritonymphs) while the maternally-acquired Cd accounted for 41% of the juvenile internal Cd load. Our results suggest that dermal adsorption of metal ions is not important for O. nitens and that maternal transfer of Cd in soil invertebrates has ecological and toxicological implications for populations of soil invertebrates. Maternal transfer should be incorporated as a criterion in setting environmental soil quality guidelines (SQGE) for cadmium and other non-essential heavy metals.

China has become one of the most serious PM₂.₅-dominated air pollution country. Despite a great deal of research has focused on analysing the influence of social and economic driving forces of PM₂.₅ pollution in China, most research in existence either applying mean regression or failing to consider the spatial autocorrelation. Motivated by this, this paper utilizes a Bayesian hierarchical spatial quantile regression method to explore the effect of socioeconomic activity on PM₂.₅ air pollution. By introducing spatial random effects into the model, the spatial autocorrelations of residuals are significantly reduced. The empirical study demonstrated that the PM₂.₅ concentration levels were strongly correlated with total population, urbanization rate, industrialization level and energy efficiency at all quantiles. For upper quantiles, the impact of urbanization rate on the haze is the greatest among all the predictors, then followed by the total population; while for lower quantiles, industrialization has the greatest impact on the PM₂.₅ concentration. The impacts of energy efficiency in the lower 15% and upper 15% quantiles are higher compared to any of the other quantiles.

The identification and quantification of pharmaceutical and personal care products (PPCPs) in aquatic ecosystems is critical to further studies and elucidation of their fate as well as the potential threats to aquatic ecology and human health. This study used mass balances to analyse the sources, transformation, and transport of PPCPs in rivers based on the population and consumption habits of residents, the removal level of sewage treatment, the persistence and partitioning mechanisms of PPCPs, hydrological conditions, and other natural factors. Our results suggested that in an urbanized river of Guangzhou City, China, the daily consumption of PPCPs was the main reason for the variety of species and concentrations of PPCPs. Through the determination of PPCPs in the river water samples and a central composite design (CCD) methodology, the dominant elimination mechanisms of caffeine and carbamazepine from river water were photolysis and biodegradation, but that of triclosan was sorption rather than biodegradation. The mass data of 3 PPCPs were estimated and corroborated using the measured data to evaluate the accuracy of the mass balance. Finally, caffeine, carbamazepine and triclosan discharged from the Shijing River into the Pearl River accounted for 97.81%, 99.52%, and 28.00%, respectively, of the total mass of these three compounds in the surface water of Shijing River. The results suggest that photolysis are the main process of natural attenuation for selected PPCPs in surface waters of river systems, and the transfer processes of PPCPs is mainly attributed to riverine advection. In addition, the low concentration of dissolved oxygen inhibited the degradation of PPCPs in the surface water of Shijing River.

Understanding the subsurface transport of perfluorooctanoic acid (PFOA) is of considerable interest for evaluating its potential risks to humans and ecosystems. In this study, packed-column experiments were conducted to examine the influence of surface roughness on PFOA transport in unsaturated glass beads, quartz sand and limestone porous media. Results showed decreasing moisture content significantly increased the air-water interfacial adsorption of PFOA and led to greater retardation in all three types of porous media. Particularly, rougher surface (limestone > quartz sand > glass beads) and smaller grain size (i.e. a larger solid specific surface area, SSSA) significantly enhanced PFOA retardation under unsaturated conditions. These results were further supported by bubble column experiments and SSSA analysis of porous media, which demonstrate that except for the factors affecting PFOA transport in solid-water interface (e.g. surface charge and chemical heterogeneity), the greater retardation of PFOA during transport is attributed to the larger air-water interfacial areas associated with rougher surface and smaller grain size and hence greater interfacial adsorption of PFOA. Our results indicated the importance of surface roughness on the retention and transport of PFOA in the unsaturated zone.